Autonomous connection switching in a wireless communication network

The present application is a continuation of U.S. patent application Ser. No. 15/114,163, now U.S. Pat. No. 10,945,181, which was filed on Jul. 26, 2016, which is a national stage application of PCT/CN2014/071844, which was filed Jan. 30, 2014, the disclosures of each of which are incorporated herein by reference in their entirety.

The present invention relates to methods for managing a connection between a user equipment and a wireless communication network and to corresponding devices.

For cellular networks, e.g., as specified by 3GPP (3rd Generation Partnership Project), handover (HO) procedures are defined which allow for maintaining an ongoing connection of a user equipment (UE) while moving between different serving cells.

For example, in the case of the LTE (Long Term Evolution) technology, such HO procedures are specified in 3GPP TS 36.331 V12.0.0 (2014-01). In these HO procedures, the UE which is in a mode referred to as “RRC_connected”, i.e., has an active connection to the cellular network, typically monitors a set of neighboring cells. These measurements may trigger sending of a measurement report from the UE to its serving base station, in the LTE technology referred to as eNB (evolved Node B). A typical example of such triggering event, referred to as “Event A3”, corresponds to the measurement result for the neighboring cell being better than the present serving cell plus an offset. The measurement result may for example be expressed in terms of Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ). The triggering event further requires that such condition is met for a certain minimum duration, specified by a parameter referred to as “timeToTrigger”. On the basis of the measurement report, the serving eNB decides whether a HO of the UE should be performed or not. When deciding to perform a HO of the UE, the serving eNB prepares the HO by sending a HO request to an eNB controlling a target cell for the HO. As a part of this HO request, the serving eNB also provides context information of the UE, e.g., concerning a current Access Stratum (AS) configuration and UE-specific Radio Resource Management (RRM) information. In response, the eNB controlling the target cell generates a HO command. The serving eNB then forwards the HO command to the UE. This is done in a transparent manner, i.e., the information provided to the UE is determined at the eNB controlling the target cell and not modified by the serving eNB. The HO command which is sent to the UE for example includes the identity, and optionally the frequency, of the target cell and RRC information common to all UEs in the target cell, such as information required to perform a random access, a dedicated radio resource configuration; a security configuration, or a cell-specific radio network temporary identity (C-RNTI) to be used in the target cell. Using such information, the UE may then proceed by performing a random access to the target cell. If the random access is successful, the UE confirms successful completion of the HO to the eNB controlling the target cell, which then becomes the new serving eNB for the UE.

In some scenarios, a network initiated HO may also be performed without a preceding Event A3 and measurement report from the UE. In such a case, the UE does not know the target cell before receiving the HO command from the serving eNB.

As can be seen, the above-mentioned known HO procedure requires rather complex interaction between the serving eNB, the eNB controlling the target cell, and the UE, which means that such a HO can be time consuming.

To meet future demands on wireless communication networks, a network deployment referred to as Ultra Dense Network (UDN) is being discussed (see, e.g., Ericsson White Paper “5G Radio Access”, June 2013, published in the Internet). For such a UDN it is suggested to use a large number of densely deployed access points (APs) and to utilize higher bandwidths and higher frequency bands than for example in the LTE technology, e.g., a bandwidth of several 100 MHz or even up to the GHz range and a frequency band in the range of 10-100 GHz.

A typical application scenario for a UDN deployment is in highly populated areas such as hot spots, office buildings, or urban centers, which may have a demand of high data rate service.

However, it can be expected that for such UDN deployment in a high frequency band weak scattering and diffraction may cause a significant attenuation difference between NLOS (non line of sight) and LOS (line of sight) radio links. Consequently, there may be a lot of areas with weak signal levels or even sudden signal outage, i.e., radio coverage holes. Accordingly, existing mobility concepts may not be adequate for such deployments. For example, the higher density of APs may result in an excessive amount of HO procedures and unacceptable signalling overhead or service degradation. Further, a sudden signal outage may even have the effect that a conventional network-initiated HO procedure as mentioned above cannot be performed, e.g., because the signal outage prevents the UE from sending the measurement report or receiving the HO command.

Accordingly, there is a need for techniques which allow for efficiently managing the connection of a UE to a wireless communication network.

According to an embodiment of the invention, a method of managing a connection between a UE and a wireless communication network is provided. According to the method, an access point of the communication network serves the connection to the UE. The access point determines a plurality of target access points. Further, the access point sends a message to the UE. The message indicates the plurality of target access points and authorizes the UE to autonomously switch the connection to one or more of the target access points.

According to a further embodiment of the invention, a method of managing a connection between a UE and a wireless communication network is provided. According to the method, a UE receives a message from an access point of the communication network, which access point currently serves the connection of the UE to the wireless communication network. The message indicates a plurality of target access points and authorizes the UE to autonomously switch the connection to one or more of the indicated target access points. According to the method, the UE further detects a triggering event. In response to detecting the triggering event, the UE switches the connection to one or more of the target access points.

According to a further embodiment of the invention, an access point for a wireless communication network is provided. The access point comprises radio interface for serving a connection to a UE. Further, the access point comprises at least one processor. The at least one processor is configured to determine a plurality of target access points. Further, the at least one processor is configured to send a message to the UE. The message indicates the plurality of target access points and authorizes the UE to autonomously switch the connection to one or more of the target access points.

According to a further embodiment of the invention, a UE is provided. The UE comprises a radio interface for establishing a connection to a wireless communication network. Further, the UE comprises at least one processor. The at least one processor is configured to receive a message from an access point of the communication network, which access point currently serves the connection of the UE to the wireless communication network. The message indicates a plurality of target access points and authorizes the UE to autonomously switch the connection to one or more of the indicated target access points. Further, the at least one processor is configured to detect a triggering event and, in response to detecting the triggering event, switch the connection to one or more of the target access points.

According to a further embodiment of the invention, a computer program or computer program product is provided, e.g., in the form of a non-transitory storage medium, which comprises program code to be executed by at least one processor of an access point for a wireless communication network. Execution of the program code causes the at least one processor to determine a plurality of target access points. Further, execution of the program code causes the at least one processor to send a message to the UE. The message indicates the plurality of target access points and authorizes the UE to autonomously switch the connection to one or more of the target access points.

According to a further embodiment of the invention, a computer program or computer program product is provided, e.g., in the form of a non-transitory storage medium, which comprises program code to be executed by at least one processor of a UE. Execution of the program code causes the at least one processor to receive a message from an access point of the communication network, which access point currently serves the connection of the UE to the wireless communication network. The message indicates a plurality of target access points and authorizes the UE to autonomously switch the connection to one or more of the indicated target access points. Further, execution of the program code causes the at least one processor to detect a triggering event and, in response to detecting the triggering event, switch the connection to one or more of the target access points.

In the following, concepts according to embodiments of the invention will be explained in more detail by referring to the accompanying drawings. The illustrated concepts relate to management of connection switching in a wireless communication network. In the illustrated embodiments, it is assumed that the wireless communication network is based on a UDN deployment. In particular, the wireless communication network may use densely spaced access points, e.g., with distances between neighboring access points in the range of 1 m to 1000 m, typically in the range of 2 m to 500 m. Further, the access points may operate in a radio frequency band between 10 GHz and 100 GHz, which means that there can be a significant difference in link quality between a LOS link and a NLOS link. However, it is to be understood that the illustrated concepts could be applied in a corresponding manner to other radio technologies, e.g., LTE, UMTS (Universal Terrestrial Mobile Telecommunications System) or Wideband CDMA (Code Division Multiple Access), or CDMA2000.

schematically illustrates structures of the wireless communication network and an exemplary UE. In particular,illustrates a plurality of access points-,-,-,-of the wireless communication network, which may be used by the UEfor connecting to the wireless communication network. Here, it should be noted that a connection between the UEand the wireless communication network may be formed by selecting an appropriate access point-,-,-,-and setting up a radio link between the UEand this access point-,-,-,-. In the exemplary scenario illustrated in, the connection is formed by a radio link to the access point-. This access point-, which maintains the active connection between the UEand the wireless communication network, may also be referred to as serving access point of the UE. In some cases, a connection may also utilize multiple radio links to different access points-,-,-,-, which may then cooperatively serve the UE.

As mentioned above, the wireless communication network may utilize a high frequency band in the range of 10 GHz to 100 GHz, in particular a frequency band above 30 GHz, such as in the range around 60 GHz. This frequency region above 30 GHz is also referred to as MMW (Millimetre Wave) band.

In such high frequency band, relatively high radio attenuation and relatively low radio diffraction have the effect that typically a LOS radio link will have significantly better quality than a NLOS radio link. However, since a LOS radio link radio link is sensitive to propagation obstacles, fast switching of the connection between different access points-,-,-,-, may be necessary to maintain the connection. For example, due to movement of the UEan obstacle may affect the LOS radio link to the access point-, which means that switching of the connection to another access point-,-,-,-is needed. Similar effects may occur in the case of moving propagation obstacles, e.g., a person moving into the LOS between the UEand the current serving access point-. Because the transition from a LOS condition to a NLOS condition may occur suddenly, there is a risk of a sudden failure of the radio link to the current serving access point-. This may in turn have the effect that the UEis no longer able to report measurements to the serving access point-and that the serving access point-is not able to send control commands to the UE. Accordingly, a conventional HO procedure as for example described in 3GPP TS 36.331 may not be applicable in these circumstances.

According to the concepts as further explained in the following, the above situation may be addressed by managing the switching of the connection between the access points-,-,-,-, in such a way that it can be autonomously performed by the UE. For this purpose, the current serving access point-may proactively send a message to the UEfor authorizing the UEto autonomously switch the connection to one or more target access points indicated in the message. Accordingly, the overall management of the connection is still network based, but the actual switching process may be performed autonomously by the UE. In the following, the above message will also be referred to as switching authorization message. The switching authorization message may be sent at an early point of time, before switching of the connection to another access point becomes necessary and while the radio link to the current serving access point-is still intact. The switching authorization message may also include information with respect to the different indicated target access points to be used be the UEwhen switching the connection to one or more of these target access points. For example, such information may include configurations of the target access points, switching conditions, usable radio resources, configurations to be used by the UEto access the target access points, or the like. The UEmay then decide whether and when to perform the switching and also select the most appropriate target access point(s) from the indicated target access points. This is accomplished in an autonomous manner, i.e., without requiring further interaction between the UEand the current serving access point-. Accordingly, fast switching of the connection is also possible in situations where the radio link to the current serving access point-fails. In this way, the illustrated concepts may allow for avoiding a service interruption due to a complete failure of the ongoing connection.

Various conditions may be evaluated by the current serving access point for triggering sending of the switching authorization message. For example, the current serving access point may perform measurements and trigger sending of the switching authorization message depending on these measurements. Such measurements may for example pertain to the quality of the radio link between the UEand the current serving access point-or to the velocity at which the UEmoves.

further illustrates the above concepts by referring to an exemplary procedure of switching the connection of the UEfrom the current serving access point-to another access point-.

In the procedure of, the connection between the UEand the wireless communication network is established at step. As illustrated, the connection is established by setting up a radio link between the UEand the access point-. The access point-thus becomes the serving access point for the UE.

At step, the access point-detects a triggering event. The triggering event may for example correspond to the establishment of the connection at step. Further, the triggering event may be based on certain measurements and/or evaluations performed by the access point-. For example, the access point-could measure and evaluate the quality of the radio link between the UEand the access point-, e.g., in terms of a channel quality indicator, beacon power level, or achievable bitrate. The triggering event could then correspond to the quality of the radio link being below a given threshold value. Further, the access point-could determine a probability of a failure of the radio link between the UEand the access point-. For example, this could be accomplished on the basis of statistical information on radio coverage holes in a radio coverage area of the access point-and on information on the position or movement of the UE. Further, the access point-could measure a velocity of the UE, e.g., by evaluating radio signals transmitted by the UE, and the triggering event could correspond to the velocity of the UEexceeding a given threshold value. In this case, it can be taken into account that a fast moving UE is more likely to require switching to another access point than a slowly moving or static UE. Further, the access point-may evaluate whether a switching authorization message which was previously sent to the UEis still valid or outdated and trigger sending the switching authorization message when the previously sent switching authorization message is no longer valid. This may for example be accomplished by providing a timer which is reset each time when the access point-sends a new switching authorization message to the UEand using expiry of the timer as the triggering event.

At step, the access point-determines a plurality of target access points which constitute candidates to which the connection between the UEand the wireless communication network may be switched. In the illustrated exemplary procedure, it is assumed that these target access points are the access points-and-. The access point-may apply various criteria for determining the target access points-,-. For example, the access point-may select access points which are located in a moving direction of the UEor access points which provide radio coverage in radio known coverage holes in the coverage area of the access point-.

The access point-then sends the switching authorization messageto the UE. This may be accomplished over a control channel supported by the radio link between the UEand the access point-. The switching authorization message indicates the target access points-,-determined at step. Further, the switching authorization messageauthorizes the UEto autonomously switch the ongoing connection to one or more of the target access points-,-indicated in the switching authorization message, without requiring further interaction between the UEand the access point-.

The switching authorization messagemay carry various kinds of information which may be used by the UEfor performing the autonomous switching of the connection. For example, the switching authorization messagemay indicate one or more conditions for triggering the switching at the UE. Such condition may for example correspond to measurements performed by the UEindicating that the expected radio link quality of one of the target access points-,-exceeds the radio link quality of the current serving access point-by a given amount. Further, such condition may correspond to measurements performed by the UEindicating that the radio link quality of the current serving access point-is below a first threshold and the expected radio link quality of one of the target access points-,-is above a second threshold. As a further example, such condition may correspond to a failure of the radio link to the current serving access point-or interruption of the connection.

Further, the switching authorization messagemay indicate information concerning each of the indicated target access points-,-. For example, such information may include an identity of the target access point-,-, e.g., in terms of an index. Further, such information may include a sequence, timing, and/or radio resources used for a beacon or pilot signal transmitted by the target access point-,-. Further, information concerning communication protocols used by the target access point may be included. Such protocol information may in particular be useful if the access points-,-,-,-,-, differ with respect to the utilized radio access technology. Further, such information may include a radio resource mapping of a control channel of the target access point-,-. Further, such information may indicate the radio access technology used by the target access point-,-. Further, such information may include system information for accessing the target access point-,-, e.g., in the form of a random access preamble or in terms of a cell-specific temporary identifier (e.g., a C-RNTI) to be used by the UE.

Still further, the switching authorization messagemay include information to be applied by the UEfor selecting between the different target access points-,-indicated in the switching authorization message, e.g., in the form of a priority order or selection policy.

The switching authorization messagemay be valid for a given time period. Such time period may be preconfigured in the UEand the access points-,-,-,-of the wireless communication network. Further, such time period may be dynamically set for each switching authorization message. In the illustrated exemplary procedure, the access point-could set the time period before sending the switching authorization messageand indicate the time period in the switching authorization message. The UEis then authorized to autonomously perform the switching while the time period has not yet expired. Expiry of the time period may be monitored by providing a corresponding timer in the UE. The access point-may set the time period for example depending on the current velocity of the UE. For example, if the UEis moving at high velocity, a shorter time period may be suitable. In certain cases, the switching authorization messagecould also be valid until a specified event, e.g., receipt of a new switching authorization message or release of the connection between the UEand the wireless communication network. In certain scenarios, the switching authorization messagemay override a previously sent switching authorization message or may be overridden by a later sent switching authorization message.

In addition to sending the switching authorization message, the access point-also provides information concerning the UEto the target access points-,-determined at step, as illustrated by messagesand. Such information may for example include a context of the UEas provided for maintaining the connection between the UEand the wireless communication network. In addition, the access point-may also start forwarding user plane data destined to the UEto the target access points-,-. In this way, the target access points-,-may be prepared to immediately continue serving the UEafter switching the connection. The information provided to the target access points-,-may also indicate the validity time period of the switching authorization message. Here, it may be beneficial to indicate a validity time period to the target access points which is larger than the validity time period applied by the UE, thereby ensuring that the target access points-,-are prepared also in cases where the UEattempts switching of the connection at the very end of the validity time period indicated to the UE. If the access point-has determined a priority order of the target access points-,-, the access point-may send the information to the different target access points-,-in the order of decreasing priority.

Upon receiving the switching authorization message, the UEmay start monitoring procedures with respect to the target access points-,-indicated in the switching authorization message. For example, the UEmay perform measurements to determine which of the indicated target access points-,-provides the highest expected radio link quality. After such determination, the UEmay continue monitoring only the target access point-,-with the highest expected radio link quality. In other scenarios, the UEmay continue to monitor all the indicated target access points-,-. The monitoring may use information provided in the switching authorization message, e.g., sequence, timing, and/or radio resources used for a beacon or pilot signal transmitted by the target access point-,-.

However, the UEperforms no immediate switching of the connection. Rather, the UEperforms switching of the connection action only in response to detecting a triggering event, as illustrated by step. Such triggering event may be preconfigured in the UEor may be indicated in the switching authorization message. For example, the triggering event may correspond to a failure of the radio link between the UEand the current serving access point-. Further, such triggering event may correspond to measurements performed by the UEindicating that the expected radio link quality of one of the target access points-,-exceeds the radio link quality of the current serving access point-by a given amount. Further, such triggering event may correspond to measurements performed by the UEindicating that the radio link quality of the current serving access point-is below a first threshold and the expected radio link quality of one of the target access points-,-is above a second threshold.

In response to detecting the triggering event at step, the UEinitiates switching of the connection to one of the target access points-,-indicated in the switching authorization message. For this purpose, the UEmay also select between the indicated target access points-,-, as indicated by step. For example, the UEmay select the target access point-,-which provides the highest expected radio link quality. In the illustrated exemplary procedure, it is assumed that the UEselects the target access point-. As illustrated by step, the UEthen performs the switching of the connection by setting up a new radio link to the target access point-selected at step, which then becomes the new serving access point for the UE.

illustrates a further exemplary procedure of switching the connection of the UEfrom the current serving access point-to another access point-. The procedure ofis in many aspects similar to that of. However, in the procedure ofa different process is used for providing the target access point-with information concerning the UE.

In the procedure of, the connection between the UEand the wireless communication network is established at step. As illustrated, the connection is established by setting up a radio link between the UEand the access point-. The access point-thus becomes the serving access point for the UE.

At step, the access point-detects a triggering event. The triggering event may for example correspond to the establishment of the connection at step. Further, the triggering event may be based on certain measurements and/or evaluations performed by the access point-. For example, the access point-could measure and evaluate the quality of the radio link between the UEand the access point-, e.g., in terms of a channel quality indicator, beacon power level, or achievable bitrate. The triggering event could then correspond to the quality of the radio link being below a given threshold value. Further, the access point-could determine a probability of a failure of the radio link between the UEand the access point-. For example, this could be accomplished on the basis of statistical information on radio coverage holes in a radio coverage area of the access point-and on information on the position or movement of the UE. Further, the access point-could measure a velocity of the UE, e.g., by evaluating radio signals transmitted by the UE, and the triggering event could correspond to the velocity of the UEexceeding a given threshold value. In this case, it can be taken into account that a fast moving UE is more likely to require switching to another access point than a slowly moving or static UE. Further, the access point-may evaluate whether a switching authorization message which was previously sent to the UEis still valid or outdated and trigger sending the switching authorization message when the previously sent switching authorization message is no longer valid. This may for example be accomplished by providing a timer which is reset each time when the access point-sends a new switching authorization message to the UEand using expiry of the timer as the triggering event.

At step, the access point-determines a plurality of target access points which constitute candidates to which the connection between the UEand the wireless communication network may be switched. In the illustrated exemplary procedure, it is assumed that these target access points are the access points-and-. The access point-may apply various criteria for determining the target access points-,-. For example, the access point-may select access points which are located in a moving direction of the UEor access points which provide radio coverage in radio known coverage holes in the coverage area of the access point-.

The access point-then sends the switching authorization messageto the UE. This may be accomplished over a control channel supported by the radio link between the UEand the access point-. The switching authorization messageindicates the target access points-,-determined at step. Further, the switching authorization messageauthorizes the UEto autonomously switch the ongoing connection to one or more of the target access points-,-indicated in the switching authorization message, without requiring further interaction between the UEand the access point-.

The switching authorization messagemay carry various kinds of information which may be used by the UEfor performing the autonomous switching of the connection. For example, the switching authorization messagemay indicate one or more conditions for triggering the switching at the UE. Such condition may for example correspond to measurements performed by the UEindicating that the expected radio link quality of one of the target access points-,-exceeds the radio link quality of the current serving access point-by a given amount. Further, such condition may correspond to measurements performed by the UEindicating that the radio link quality of the current serving access point-is below a first threshold and the expected radio link quality of one of the target access points-,-is above a second threshold. As a further example, such condition may correspond to a failure of the radio link to the current serving access point-or an interruption of the connection.

Further, the switching authorization messagemay indicate information concerning each of the indicated target access points-,-. For example, such information may include an identity of the target access point-,-, e.g., in terms of an index. Further, such information may include a sequence, timing, and/or radio resources used for a beacon or pilot signal transmitted by the target access point-,-. Further, information concerning communication protocols used by the target access point-,-may be included. Such protocol information may in particular be useful if the access points-,-,-,-,-differ with respect to the utilized radio access technology. Further, such information may include a radio resource mapping of a control channel of the target access point-,-. Further, such information may indicate the radio access technology used by the target access point-,-. Further, such information may include system information for accessing the target access point-,-, e.g., in the form of a random access preamble or in terms of a cell-specific temporary identifier (e.g., a C-RNTI) to be used by the UE.

Still further, the switching authorization messagemay include information to be applied by the UEfor selecting between the different target access points-,-indicated in the switching authorization message, e.g., in the form of a priority order or selection policy.

The switching authorization messagemay be valid for a given time period. Such time period may be preconfigured in the UEand the access points-,-,-,-,-of the wireless communication network. Further, such time period may be dynamically set for each switching authorization message. In the illustrated exemplary procedure, the access point-could set the time period before sending the switching authorization messageand indicate the time period in the switching authorization message. The UEis then authorized to autonomously perform the switching while the time period has not yet expired. Expiry of the time period may be monitored by providing a corresponding timer in the UE. The access point-may set the time period for example depending on the current velocity of the UE. For example, if the UEis moving at high velocity, a shorter time period may be suitable. In certain cases, the switching authorization messagecould also be valid until a specified event, e.g., receipt of a new switching authorization message or release of the connection between the UEand the wireless communication network. In certain scenarios, the switching authorization messagemay override a previously sent switching authorization message or may be overridden by a later sent switching authorization message.

Upon receiving the switching authorization message, the UEmay start monitoring procedures with respect to the target access points-,-indicated in the switching authorization message. For example, the UEmay perform measurements to determine which of the indicated target access points-,-provides the highest expected radio link quality. After such determination, the UEmay continue monitoring only the target access point-,-with the highest expected radio link quality. In other scenarios, the UEmay continue to monitor all the indicated target access points-,-. The monitoring may use information provided in the switching authorization message, e.g., sequence, timing, and/or radio resources used for a beacon or pilot signal transmitted by the target access point-,-.

However, the UEperforms no immediate switching of the connection. Rather, the UEperforms switching of the connection action only in response to detecting a triggering event, as illustrated by step. Such triggering event may be preconfigured in the UEor may be indicated in the switching authorization message. For example, the triggering event may correspond to a failure of the radio link between the UEand the current serving access point-. Further, such triggering event may correspond to measurements performed by the UEindicating that the expected radio link quality of one of the target access points-,-exceeds the radio link quality of the current serving access point-by a given amount. Further, such triggering event may correspond to measurements performed by the UEindicating that the radio link quality of the current serving access point-is below a first threshold and the expected radio link quality of one of the target access points-,-is above a second threshold.

In response to detecting the triggering event at step, the UEinitiates switching of the connection to one of the target access points-,-indicated in the switching authorization message. For this purpose, the UEmay also select between the indicated target access points-,-, as indicated by step. For example, the UEmay select the target access point-,-which provides the highest expected radio link quality. In the illustrated exemplary procedure, it is assumed that the UEselects the target access point-. As illustrated by step, the UEthen performs the switching of the connection by setting up a new radio link to the target access point-selected at step, which then becomes the new serving access point for the UE.

When switching the connection at step, the UEalso indicates an identity of the previous serving access point-, e.g., in terms of an index, to the new serving access point-. The new serving access point-may then use this identity to send a requestfor information concerning the UEto the previous serving access point-.

In response to the request, the access point-provides information concerning the UEto the new serving access point-, as illustrated by message. Such information may for example include a context of the UEas provided for maintaining the connection between the UEand the wireless communication network.

The connection switching procedures as explained above may also be used together with other kinds of connection switching procedures, e.g., a connection switching procedure in which the UEis instructed by the current serving access point to immediately switch to a certain target access point. In such cases, the autonomous switching procedure could be used as a backup for cases where an instruction for immediate switching is not possible, e.g., due to a failure of the radio link between the UEand the current serving access point. Accordingly, if the UEfirst receives the switching authorization message and then a command for immediate switching of the connection, the UEmay first attempt to perform the immediate switching and, if this immediate switching fails, continue with the autonomous switching procedure.